Transcript Earth’s Crust - Ste. Genevieve R

Earth’s Crust
Convection
currents
Continental drift – idea that continents
have moved slowly to their current
positions due to convection currents
in the mantel.
Pangea – the idea that the all land
masses on earth were once a single
large land mass.
Ocean floor spreading – theory that
hot less dense material below Earth’s
crust rises toward the surface at the
mid-ocean ridges. Then, it flows
sideways, carrying the seafloor away
from the ridge in both directions.
http://geology.com/nsta/divergent-boundary-oceanic.gif
Convection current – unequal
distribution of heat in the mantel
causes a net movement in a circular
motion.
The Earth’s CRUST is the outer most part of
the Earth’s surface.
• Average 32 km thick
• Thickest point 70 km (in mountains)
• Thinnest point 8 km (under ocean)
Plate tectonic – theory that Earth’s crust and part
of the upper mantle are broken into sections
called plates.
Lithosphere – all of the earth’s crust and part of
the upper mantle.
http://www.allaboutspace.com/subjects/astronom
y/planets/earth/Inside.shtml
Asthenosphere – plastic like layer below the
lithosphere. The ridged plates of the lithosphere
“float” on the more plastic layer called the
asthenosphere.
l
Deformation – The breaking, tilting, and
folding of crustal rock due to crustal
movement. (three types of forces)
1. Compression – squeezing of earth’s
crust that compacts the rock.
Convergent boundary
2. Tension – is the pulling apart of the
earth’s crust. Divergent boundary.
3. Shearing – pushes rocks side by
side in opposite directions.
Transform boundary.
Convergent boundary
Divergent boundary
Transformation boundary
Rift valley
subduction
FAULTS
Normal Fault – fault caused by tension
stress that moves the hanging wall down
relative to the foot wall.
Reverse Fault – fault caused by
compression forces where the hanging
wall will move up relative to the foot wall.
In Lateral (strike-slip) faulting, the two blocks
move either to the left or to the right relative to
one another. Strike-slip faults are associated with
crustal shear.
Thrust Fault – is formed when compression
causes the hanging wall to slide over the foot
wall. (almost horizontal movement)
Facts about folds/faults.
1. increased temp. =‘s fold
2. decreased temp =‘s fault
3. increased pressure =‘s fold
4. decreased pressure =‘s fault
5. rock type – brittle =‘s fault
6. rock type – ductile =‘s fold
7. time – greater the time =‘s fold
8. time – less time =‘s fault
Fault block mountain is a mountain created by
blocks of rock uplifted by normal faults.
Rift Valley are valleys created when a block of
land between two normal faults slide downward.
• End of chapter 10
Folds – are bends in rocks without breaking
• folds have two parts
1. Anticline – upward part of fold
2. syncline – downward part of fold
Anticline
Plateau – is a large area of flat land that is raised
high above sea level. Usually bordered by cliffs or
mountains.
Domes – is the uprising area caused by magma
Floating crust -
more dense
less dense
•A balance exist between the downward force of
the crust and the upward force of the mantle
called ISOSTASY.